ETF2009 Shootout

The ETF2009 shootout was a contest of single-ended output transformers. Scroll down to see the results and pictures.

THE RULES

 The test amplifier will be a 310A+300B "l'audiophile" (without negative feedback), and the speaker will have high sensitivity, passive crossover, more or less 8 ohm impedance.

 The shootout listening tests will be MONOPHONIC : there is no need to bring a pair of identical transformers, one is enough.

 The B+ voltage is about 430VDC, and the primary will have to handle 70mA DC.

The negative tap of the secondary will be joined to earth.

 The impedance ratio can go from 2.2K / 8 ohm to 3.6K / 8 ohm.

The test amplifier has 4 female 4mm banana plug (IEC 1010 compatible) :

B+ (high voltage 430VDC) : Red

P (plate of the 300B) : Yellow

0 (earth of the amplifier, and negative input of the speaker) : Black

8 (positive input of the speaker) : White

How to register to the shootout ?

1. First of all, you have to register to the triode festival :  http://www.melaudia.net/subscribeETF.php
2.  On your registration form, fill the "participate to the shootout with" field with the name of your transformer (brand and reference, or any description if it is a DIY transformer)
3.  Bring one transformer with the cords+ 4mm banana plug at ETF

Participants are asked to :

 Make sure that the transformer is not phase-inverting (but it is not disqualifying)

clearly identify each tap that plugs into the test amplifier (color and/or name)

provide 0.5 to 1m cords with 4mm male banana  (IEC 1010 is recommanded)

Pay attention to insulation problems :

• Please provide B+ / Plate wire with 600VDC insulation at least.
• If you have any doubt about isolation of your wires on primary side, please add some thermo sleeve around those both.
• Secondary wire are grounded, so isolation is not an issue.

Before the shootout, the following tests will be performed :

1. a 500V insulation test between B+ and 0 tap.
2. turn ratio measurement.
3. phase/out-of-phase check.

Special stuff :

Parafeed transformers (choke + condensator + transformer without air gap) are authorized.

DIY transformers are especially welcomed, but here again, pay attention to insulation.

mismatchs (5K to 16 ohm, used as 2.5K to 8 ohm, for instance) are authorized, but please indicate clearly which secondary tap you want to plug on the speakers, and which primary tap you want to use.

primary and/or secondary compensations are authorized (zobel network or whatever you want, providing it is not dangerous)

Sorry, negative feedback is forbidden.

 THE SETUP

Krell CD Transport and Wadia D/A converter

The WE310A+WE300B amplifier used for the shootout. There is no output transformer, but two sets of banana female plugs: B+ (red), 300B Plate (yellow), ground (black) and 8 ohm (white). A switch connects the transformer A or B.

The mono line preamp used for the shootout. Sowter multitap transformer for the volume, Tango output transformer (500 or 600 ohm external load).

A 10 turns 500 ohm potentiometer was used to calibrate the output level of each transformer. It is also the external load of the preamplifier.

The loudspeaker used for the shootout : Great Plain Audio 515 and 399, with Westrex acoustilens horn.

31 transformers ready for the shoot-out !!!

THE RESULTS

list of participants :

some pictures of the transformers :

THE WINNER

Peter van Willenswaard (right) won with an Audionote Trans-300 double-C-core, and receives a pair of TJ 300B from Julien (left).

The measurements

Jean-Michel measuring a transformer. Measurements (distortion, bandwidh, impulse response) have been made with 70mA through the primary.

See the measurements here .